<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #box{
      width: 70vw;
      height: 70vw;
      background: red;
      font-size: 10vw;
      color: #fff;
    }
  </style>
</head>
<body>
  <div id="box"></div>
  <script>
    /**
     * -changedTouches 触发当前事件的手指列表
     * -targetTouches  当前元素的手指列表
     * -touches   当前屏幕中的手指列表
     */
    let box = document.querySelector('#box')
    document.addEventListener("touchstart", e=>e.preventDefault(),{passive:false})
    box.addEventListener("touchstart", () => {
      console.log("start")
    })
    box.addEventListener("touchmove", (e) => {
      box.innerHTML = `
        触发事件的手指个数 ${e.changedTouches.length}<br/>
        当前元素上手指个数 ${e.targetTouches.length}<br/>
        当前屏幕手指个数 ${e.touches.length}
      `
    })
    box.addEventListener("touchend", () => {
      console.log("end")
    })
  </script>
</body>
</html>